A Child’s Drawing Tucked in an Agatha Christie Book Is Its Own Mystery

“A colleague once found a piece of bacon, cooked, as a bookmark,” Ms. Thorne said. “I’m a vegetarian, so I really object to that.”

Usually when librarians come across lost items in books, they will leave them in the library’s lost and found, she said, so it was curious that the card was still in the book. How the Mother’s Day card had made it all the way across the Atlantic Ocean was a “right little mystery,” she said.

“That’s the joy of all these reselling sites,” she said. “Books can go anywhere in the world.”

Carl Turner, a spokesman for the Norfolk County Council, which runs Norfolk’s library system, said this particular copy of “The ABC Murders” was believed to have belonged to the Millennium Library in Norwich. But books move around the system, he said, so its last location could have been anywhere in the county.

As any modern day detective tackling a mystery would do, Ms. de Sturler took the case to the internet, posting about the card on her blog, but online sleuths failed to produce any promising leads. Then a British friend of Ms. de Sturler decided to reach out to the BBC in Norfolk.

Suddenly, Ms. de Sturler was on the air in Agatha Christie’s home country, making a direct appeal to radio listeners in Norfolk for any information that might help reunite the card with Kit, or Kit’s Mum. Amy Blunt, the BBC journalist who first reported the story, said she could picture Kit’s mother kicking herself for losing track of the card but believed that the community would crack the case.

“I’m hopeful because the people of Norfolk, we’re a lovely bunch,” she said. “And you can just hear the collective, countywide ‘Aww.’ So if anyone’s going to do it, it’s us. We’ll reunite them, hopefully.”